Aluminum copper alloy



Patented Jan. 18, 1949 ALUMINUM COPPER ALLOY Tennyson Fraser Bradbury, Darley Abbey, England, assigno'r to Rolls-Royce Limited, Derby,

1 England NbDrawihg. Application February 8, 1945, Serial No.1- 57.6;903. In Great Britain February 25,

This invention relates to aluminium base alloys.

1 have discovered that an alloy of the undermentioned composition in the worked state if given a solution treatment of from 535 to 545 C. for a period at least of hours, quenched in 4 Claims. (Cl.148-32.5.)

water of a temperature less than 100 C. and aged at a temperature of about 200 C. for at least 10 hours has specially valuable qualities.

. The. ageing time preferably varies between 10 and 30jhours. and is carried out at a temperature lof.about,200 and preferably between 210 and .220? 0.; Ageing may be continuedbeyond 30 hours butthere does not appear to be any advantage in'lfso doing. The alloy is of the following composition:

Percent of the whole Copper 1 i 5.0 -'I.0 Titanium r 0.01-0.6 Manganese -1 0.01-1.0

Silicon and iron not exceeding together 0.8 Balance essentially aluminum.

The expression aluminium the remainder in the claims is not intended to exclude the usual traces of impurities or elements used in the normal refining processes.

One or more other elements which have modifying or degasefyin or grain refining qualities namely, sodium, silver, barium, zinc, the rare earths, vanadium, niobium, chromium, tellurium, cobalt, zirconium, antimony, beryllium, bismuth, boron, cadmium, calcium, lead, lithium, molybdenum, tungsten, thallium and thorium (hereinafter referred to as improving elements) may be used up to a maximum of 0.5 per cent of any one of them and 0.75 per cent in total.

By the worked state is meant forged, extruded or otherwise mechanically worked.

By the use of the treatment above given I am able to tolerate iron and silicon up to a combined total of 0.8 per cent and thereby avoid the necessity of using super purity metal as a basis for my alloy.

The alloy is particularly suitable for pistons of high duty aircraft engines which experience high stresses.

It has been found necessary in recent years (due to increased stressing of pistons in high duty aero engines) to reduce or eliminate internal stresses caused by solution-treatment quenching, and this has been accomplished by boiling-water quenching. However, the hot strength and hardness is lowered compared with the same alloy,

quenched in water below 100 C.

Boiling water quenching would very considerably lower the hot strength properties of my alloy, but I have found thata combination of water quenching at a temperature above room temperature, but below the boiling point, followed by ageing at a temperature of about 200 C., produces no more internal stress than boiling water quenching the normal piston alloys like Y alloy (containing 3.5-4.5 Cu, 1.0-2.5 Ni, 0.5-2.0 'Mg. up to 0.5 Fe, up to 0.2 Ti, upto 0.5 Si and up to 1.0 Mn) or that made to British standards specification 11.42 (containing1.5-3.0 Cu, 0.5-1.5 Ni-,;1.2-1.8 Mg. 1.0-1.5 Fe, up to 0.2 Ti andup to 1.3 Si), For the best hot strength, a solution temperature of 535-540". C. is preferred, and the preferred temperature of "the water is between 70-95 C.

Thisphenomen'o'n appears to be peculiar to my alloyand has been found to be due to a volume change which takes place on quenching, so that in the quenched state the volume occupied is less than in the forged state. In order for the volume to attain the :same as in the forged state, it is necessaryyto age by heating at temperatures of about 200" C. and. over for a period exceeding 10 hours. I i

,61' diameter pistonsgiven the ageing temperature recommended in mysaid previous application have been found to grow in service 10-12 thousands of an inch thus causing pick up and seizure. The treatment now proposed ensures that the growth takes place during the ageing treatment and having taken place the dimensions attained are maintained even after lon running service.

An alloy of the following composition:

Per cent Copper 5.6 Titanium 0.18 Manganese 0.25 Silicon 0.18 Iron 0.25

was given solution treatment at 535 to 540 C. for times ranging between 1 and 30 hours and aged for 16 hours at 215 C. The test pieces were then soaked for hours at 300 C. to simulate the conditions of temperature which a piston would experience in service and the tensile strength and Brinell were taken at this temperature. After cooling to room temperature the recovery Brinell was taken.

The following table gives the results:

What I claim is: 1. An aluminium alloy of the following composition:

Per cent of the whole Copper 5.0 -7.0 Titanium 0.01-0.23 Manganese 0.01-1.0

Silicon and iron not exceeding together 0.8 Aluminium the remainder,

Per cent of the whole Copper 5.0 -7.0 Titanium 1 0.01-0.51 Manganese 0.01-1.0

Silicon and iron not exceeding together 0.8 Aluminium the remainder,

in the worked state which comprises subjecting the alloy to solution treatment from 535 to 545 4. The process of improving an aluminium aly of the following composition:

Per cent of the whole Copper 5.0 -7.0 Titanium 0.01-0.5 Manganese 0.01-1.0

Silicon and iron not exceeding together- 0.8 Aluminium the remainder,

in theworked state which comprises subjecting the alloy to solution treatment from 535 to 540 C. for a period of at least 10 hours quenching in 1 water of a temperature of above room temperature but less than 100 C. and ageing at about 200 C. for at least ten hours.

C. for a period of at least 10 hours quenching in water of a temperature between '70 and C. and ageing at about 200 C. for at least 10 hours.

TENNYSON FRASER BRADBURY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,352,322 Stay Sept. 7, 1920 1,508,556 Jefiries et a1. Sept. 16, 1924 1,876,917 Gosslaw Sept. 13, 1932 2,040,324 Moore May 12, 1936 2,041,042 Bates May 19, 1936 2,062,329 Nook Dec. 1, 1936 FOREIGN PATENTS Number Country Date 309,586 Great Britain Mar. 27, 1940 650,982

France Feb. 13, 1929 

